UPTAKE AND DISTRIBUTION OF CALCIUM AND PHOSPHORUS IN BEECH (FAGUS-SYLVATICA) AS INFLUENCED BY ALUMINUM AND NITROGEN

We studied the effects of excess nitrogen added as nitrate (NO3-) or a mmonium (NH4+), or both, on mineral nutrition and growth of beech (Fag us sylvatica L.) plants grown at pH 4.2 in Al-free nutrient solution o r in solutions containing 0.1 or 1.0 mM AlCl3. A high external concent ration of NH4+ increased the concentration of nitrogen in roots, stems and leaves. The root/shoot dry weight ratio was less in plants grown in the presence of NH4+ than in plants grown in the presence of NO3-. The concentration of phosphorus in the roots was increased and the con centration of potassium in all parts of the plant was decreased by NH4 +. A high external concentration of NO3- caused a decrease in phosphor us concentrations of the root, stem and leaf. Uptake of Ca-45(2+) by r oots was reduced in the presence of high concentrations of NH4+ or NOS , and a combination of high concentrations of nitrogen and aluminum fu rther reduced the uptake of Ca-45(2+). Uptake of phosphate (P-32) and concentrations of phosphorus in root and shoot were increased when pla nts were grown in the presence of 0.1 mM Al. Exposure to 1.0 mM Al, ho wever, reduced the concentration of phosphorus in roots and shoots and the reduction was greater when plants were grown in the presence of a high external NO3- concentration. Aluminum binds to roots, and plants grown in the presence of 1.0 mM Al had a slightly higher concentratio n of aluminum in roots than plants grown in the presence of 0.1 mM Al, whereas the concentration of Al in the shoot was increased 2 to 3 tim es in plants exposed to 1.0 mM Al. Furthermore, the effects of 1.0 mM Al on uptake of other macronutrients were quite different from the eff ects of 0.1 mM Al. We conclude that 0.1 mM Al facilitates uptake and t ransport of phosphorus in beech and that between 0.1 and 1.0 mM Al the re is a dramatic change in the effects of Al on uptake and transport o f divalent cations and phosphorus.